Complete MG Remission Seen as More Likely in Robot-assisted Thymectomy

Surgery to remove the thymus gland, a procedure often recommended to people with myasthenia gravis whether or not tumors exist, is more likely to result in complete disease remission when the surgery is assisted by robots, a study found.

The study, “Improvement in symptom remission rate following robotic thymectomy in patients with myasthenia gravis,” was published in the journal Interactive CardioVascular and Thoracic Surgery.

Myasthenia gravis (MG) is an autoimmune disease in which immune cells mistakenly attack the connections between muscles and nerve cells, causing muscular weakness and fatigue.

Studies also point to the thymus gland — a component of the immune system — as contributing to MG. Though scientists have not yet determined the role the thymus plays in this disease, its association seems likely, as 15% of MG patients have a thymoma, or a tumor in the thymus.

For those with such tumors, a thymectomy — surgery to remove the thymoma along with rest of the thymus — is the recommended course of action.

A clinical trial (NCT00294658) that concluded in 2015 found that surgical removal of the thymus can also ease MG symptoms in patients who do not have an underlying thymoma. And other studies have reported that symptom remission is more commonly achieved after a thymectomy in MG patients who do not have a thymoma.

As a result, a thymectomy is a now common consideration for those with MG.

The traditional technique for a thymectomy is called transsternal thymectomy (TST). This approach is similar to open heart surgery, in that the sternum (breastbone) is opened, so surgeons gain access to the thymus. However, relatively high rates of complications are associated with TST.

Modern techniques, including video assisted thoracic surgery (VATS) and robotic assisted thoracic surgery (RATS), have been shown to lessen post-operation pain and blood loss, shorten hospital stays, and lower complication rates.

In both techniques, a camera is inserted into the patient’s chest to assist surgeons. Their main difference is that RATS also uses a surgical robot to perform the surgery.

Physicians at the Helsinki University Hospital in Finland started using VATS in 1998, with the exception of particularly large thymomas that required the use of conventional TST. They switched to RATS as their preferred approach for thymectomies in 2009.

Now, investigators at this hospital and colleagues in the U.S. studied short- and long-term clinical outcomes in MG patients given a thymectomy using VATS or RATS.

They included data from 147 MG patients who underwent thymus removal surgery at Helsinki University Hospital from 1999 to 2015. Of these, 86 (59%) had a surgery with VATS and 61 (42%) with RATS.

Blood loss during surgery and the operation’s duration were similar in both groups. But those whose surgery included RATS had a shorter post-surgical hospital stay (median of two days), compared to those who had VATS (median of three days).

Both VATS and RATS were considered safe and successful techniques for thymectomy, “with a low rate of complications and a short hospital LOS [length of stay]”.

Rates of complete remission at follow-up were higher among those who had RATS (26%), compared to those who had VATS (18%). To be in complete remission, patients must remain symptom-free for at least one year and without taking pyridostigmine.

Researchers also found that patients who were younger, and/or had entered into remission before surgery, had higher chances of  a complete remission at follow-up.

The considerable experience of doctors at this hospital with assisted thymectomies could be a contributing factor to the higher success rate of RATS compared to VATS, the study noted.

“Our RATS programme was established after 10 years of experience with VATS thymectomy, and so RATS patients have almost certainly benefited from the accumulated institutional experience in MIS [minimally invasive surgery],” the researchers wrote.

Another potential source of bias, they added, might stem from the unequal follow-up period between the two groups. Those who had RATS were followed for a median of five years, whereas those who had VATS were monitored for a median of 12 years, allowing for an increased possibility of relapse.

Nevertheless, investigators pointed out that RATS allows for greater precision and more successful removal of the thymus than does VATS.

“[O]ur results show that RATS thymectomy, along with younger age and preoperative MR [medical remission], is associated with greater likelihood of MG remission. Perioperative outcome is excellent in both methods. Prospective trials are needed to confirm these results,” the researchers wrote.